An increased knowledge of the biology of plant cells is important in the understanding of biology in human cancer from several points of view. 1. Plant cancers elicited by crown-gall bacteria have been well studied and provide an experimental system not available in animal cancer biology. This includes possible isolation of the oncogen, an analysis of its information, and a step by step outline of the process and transformation. Since all plants can be regenerated from single cells, it is also possible to study the factors that effect reversion of normal plant cells from previously transformed cells. 2. Plant secondary products are often found to be of use in therapeutic treatment of human cancer. These products are produced by unique chemical reactions that exist only in plants. Plant cell culture should allow major cell production of such compounds much as in the production of antibiotics from microbial fermentation. 3. A number of cancers are found to be linked with human nutrition. A further understanding of plant biology should help us to discern what these agents are in the food chain and what biological role they play in higher plants. We may also learn how to modify their presence in human foodstuffs.